(1) Field of the Invention
The invention relates to the use of an anisotropic conductive film, having conductive particles in an insulating adhesive, with tape automated bonding to form interconnections between a lead array and an integrated circuit element with composite bump input/output pads. The use of an anisotropic conductive film provides a bonding process with reduced temperature and pressure and a reliable encapsulated bonded structure. The use of the composite bump input/output pads on the integrated circuit element allows the interconnection to be made with reduced bonding force.
(2) Description of Related Art
In conventional tape automated bonding high temperatures are required to form the bond between the inner lead ends of a lead array and the bonding pads on an integrated circuit element. The difference in thermal expansion between the elements of the assembly can distort the lead array and make subsequent processing, such as bonding the outer lead ends, difficult. This invention provides a method to avoid this problem by using an anisotropic conductive film in combination with tape automated bonding and composite bump input/output pads on an integrated circuit element. The anisotropic conductive film comprises conductive particles in an insulating adhesive.
U.S. Pat. No. 4,963,002 to Tagusa et al describes a connection construction using conductive particles and both conductive and insulating adhesives. Japanese Patent 3-62927 to Fujimoto describes a composite conductive particle, an adhesive layer, and flip chip bonding.
U.S. Pat. No. 5,001,542 to Tsukagoshi et al. describes a board made of glass, synthetic resin, metal ceramic or their composite materials. Tsukagoshi et al. use a combination of conducting particles, insulating particles, and an adhesive to form the electrical bond. The conducting particles are metal such as nickel, silver or gold. The Invention of this Patent Application uses an anisotropic conducting film having composite bumps in an insulating adhesive. The composite bumps have a polymer body covered by a conductive metal coating.
U.S. Pat. No. 4,470,657 to Tsukagoshi et al. describes the use of an anisotropic conductive film using an adhesive with conductive particles of multiple sizes.
U.S. Pat. No. 4,731,282 to Tsukagoshi et al. describes insulating adhesives.